1. Field of the Invention
The present invention relates to a mobile machine arrangement for exchanging individual or groups of old ties for individual or groups of new ties in a track consisting of two rails fastened to ties and supporting respective machine frames for mobility in an operating direction, each machine frame being supported on the track by undercarriages, being propelled along the track and carrying a tie exchange device comprising power-driven vertically and longitudinally adjustable tie gripping means, the tie exchange device on a leading machine frame, in the operating direction, being arranged for laterally pulling old ties out of the track and the tie exchange device on a trailing machine frame being arranged for laterally inserting new ties into the track.
2. Description of the Prior Art
U.S. Pat. No. 4,253,398, dated Mar. 3, 1981, discloses a mobile apparatus for the continuous replacement of ties with which all the ties of a track are sequentially exchanged as the apparatus advances continuously while the rails are raised and spread apart above a section where the ties are exchanged. This apparatus has been successfully used for the complete exchange of all ties.
U.S. Pat. No. 4,511,541, dated Sept. 16, 1986, discloses a continuously advancing ballast cleaning machine which comprises the tie pullers and inserters operated while the track is lifted and the ballast is excavated, cleaned and returned to the track bed. The two tie exchange devices are mounted on the machine frame between two swivel trucks supporting the machine frame ends and are longitudinally displaceable in the direction of elongation of the machine frame. The tie exchange devices are utilized only along a section of the track ahead of, at and behind obstacles extending along a shoulder of the track while the machine continuously advances. In other words, these tie exchange devices are only auxiliary means on the ballast cleaning machine to enable the ballast excavating chain to operated properly when lateral obstacles are encountered along the track and while the track is lifted to enable the ballast to be excavated. There is no indication in the patent how and from where to control the operation of the tie exchange devices since no operator's cab for these devices is discernible.
It is also known and widely practiced, particularly in Australia and the United States of America, to exchange only individual ties or groups of adjacent ties in an existing track while retaining the old ties between the exchanged ties. Such partial tie exchanges are repeated every few years so that eventually all the old ties are replaced by new ties in the track. A mechanized tie gang for such a partial tie exchange has been disclosed on pages 22 to 24 of "Railway Track & Structures", November 1983. It comprises 24 pieces of equipment spaced from each other along the track and operating independently of each other to execute not only the tie exchange but also additional work, such as tie transport, tie cutting, ballast regulating and the like. The pulled and optionally cut ties are placed on the shoulder along the track and then moved onto a tie loading car. Similarly, the new ties are deposited from tie loading cars on the track shoulder and then inserted in the track. The ties may be transported, loaded and/or unloaded at times other than the time of the tie exchange.
A great variety of the tie exchange devices are known, which have a crane- or boom-like frame equipped with a tie gripping tong which may be operated by a clamping drive. U.S. Pat. No. 4,579,060, dated Apr. 1, 1986, for example, discloses such a tie exchange device cantilevered to a front end of a work car and comprising a power-operated pivotal crane carrying a tie gripping head actuated by a hydraulic cylinder-piston drive. The large dimension of the crane in comparison to the relatively small work car makes this machine rather labile and the structure is rather complex. In addition, the lateral pulling of an old tie out of the track and the lateral insertion of a new tie into the track is difficult because the weight of the car is transmitted to the track by an undercarriage immediately adjacent the tie being replaced. Also, the compound clamping head is designed for simultaneously gripping a new tie and an old tie to enable the clamping head to pull an old tie and insert the new tie in two subsequent operations. This makes the tie exchange operation quite difficult for the operator and, in addition, the unbalanced weight of the crane at one side of the car interferes with an accurate, rapid and trouble-free tie exchange operation. The apparatus can be used only for the spot exchange of individual ties, the old ties being usually placed on the track shoulder whence the new ties are then picked up by the clamping head for insertion. This equipment has quite a limited tie exchange capacity. Such small cars usually are not self-propelled and they can be moved along the track only at low speed.
Another type of a bidirectionally operative tie exchanging apparatus has been disclosed in U.S. Pat. No. 4,418,625, dated Dec. 6, 1983. This apparatus comprises a railroad car supported by undercarriages for mobility on the track. A telescopingly retractible tie gripping device is mounted between the undercarriages at each lateral side of the car frame. The vertically and transversely adjustable device has a clamping drive. Individual ties may be laterally pulled out of, or inserted into, the track at each said of the car. The apparatus provides no monitoring or control possibility for the two tie gripping devices, no operator's station being arranged within view of the devices. Presumably, they are actuated by an operator standing on a respective track shoulder. The capacity and accuracy of this apparatus is also rather limited because of the inadequacy of the control and the intermittent advance of the machine from tie to tie. Since the space between the track and the frame of the railroad car is quite small, the construction of the tie exchange apparatus must be very compact. A mobile installation must precede and follow the tie exchange car to transport the old ties placed on the shoulder and to transport the new ties for placement on the shoulder, which may be done simultaneously with the tie exchange or at a later time.
German patent application No. 2,230,202, published Aug. 16, 1973, discloses a machine for removing ballast from a track bed, which comprises a machine frame and power-driven vertically and transversely adjustable ballast scarifier tools mounted on a forwardly projecting end of the machine frame. A power-driven longitudinally displaceable push rod precedes the plate-like ballast scarifier tools for engagement with a respective tie for displacing the tie in the direction of the track whereby ballast may be moved to a respective shoulder under the displaced tie over the ballast scarifier tool.